There is some schematics mess here but I think m4268588 is refered on your initial circuit..

e.g. Pots wired on VDD (instead of GND) and MAIN_OUT & COMPR_OUT in differential mode (instead of addition)

Quote from: antonis on September 06, 2024, 04:39:58 AMThere is some schematics mess here but I think m4268588 is refered on your initial circuit..

e.g. Pots wired on VDD (instead of GND) and MAIN_OUT & COMPR_OUT in differential mode (instead of addition)

Now I'm confused    is the last of my uploaded schematics viable for prototyping or?

Quote from: Haraka on September 06, 2024, 06:30:44 AMNow I'm confused   

You're not alone...

I think m4268528 means something like below:



Pots grounding (instead of VDD) is already done so focus on MAIN & COMPR OUTS wiring around U5A..

edit: Forget all of the above.. You've already made those mods..

Quote from: Haraka on September 05, 2024, 02:27:20 AMThanks you guys for having the patience to help fix my mistakes!

Here is the revised schematic, is the design now in accordance with your comments?
The series resistor is 47R 1/2W, the LPF is about 34Hz (in accordance with the rule that the maximum frequency is 50Hz? And 1/2W just for dissipation reasons. If in the worst case scenario the pedal uses 100mA (I never understood how the current consumption is assumed  ) that yields power dissipation of 0,47W.

Thanks once again!

I think this looks like it should work - at least, with a few tweaks as just mentioned by Antonis. However, it looks like it could probably be simplified a lot.
Page one has a lot going on, but not a lot that you could trim.
Page two uses C15 as a power supply cap, and R20/R22/C20 to make a Vbias supply. This is a duplicate of the "Vdd" supply you've got on page five, so unless there's a good reason to keep it separate, you could get rid of all those parts and use Vdd instead.
Page three is the one where I'd look for most simplifications. There's a gain stage followed by a 4049 inverter drive stage. That part is ok, although I'd wonder if you can't put the gain in an earlier stage instead to remove one op-amp there. The part following the 4049 looks the most likely to be able to be reduced to me. I'd model this in LTspice and see what the overall frequency response looked like, and then see if I couldn't create the same response in a simpler way. There's three op-amps there where there might be able to be only one.
Page four has a inverting mixer stage followed by a gyrator-based EQ. All fair enough, although U6D does nothing, so you've got a spare op-amp that you could use elsewhere in the circuit if you can remove some of the others from the earlier pages.

Hope this helps

Eagle eye, Tom..!!!

@Haraka:  That spare U2D could be used for VDD stabilization..

The output impedance of U4A(4049) varies depending on whether U4A clips or not. In other words, omission of U3B changes the operation.

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It's possible to transform cascaded 2nd-order filter (including Bridged-T) to a 4th-order filter, but I don't know the mathematically correct procedure. (do you know?)

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If the crackling noise when the pot rotates, it may be a solution by adding some components.

Quote from: m4268588 on September 06, 2024, 09:40:25 AMThe output impedance of U4A(4049) varies depending on whether U4A clips or not. In other words, omission of U3B changes the operation.

That only means that it needs to be followed by something with a high input impedance so that the effect isn't important. A buffer like OP has is one passibility, but any non-inverting stage could work too.
Anyway, how much does it vary? There's a 10K in series with that output, so it'll need to be quite a lot to swamp that.

Once again thanks everybody I cannot overstate how I appreciate your help!

1. As said I've already done the modifications so that was left alone 

2. U2D was implemented to stabilize VDD, didn't event think of that thanks @antonis!

3. @ElectricDruid thanks for the observation for using VDD!   unfortunately, it was left as an artefact of implementing the dirt cheap compressor schematic  , also U6D I had no other idea what to do with it, maybe as implementing an "Direct output" but that should require 2 op-amps? so I inserted him as a 6-band eq for 5kHz.

4. Should I implement a "master volume" pot after eq?If yes how is it the best to do? Or is that totally unnecessary?

Here is the revised schematic (with new annotations to accommodate the component changes)

Quote from: Haraka on September 09, 2024, 04:28:46 AMShould I implement a "master volume" pot after eq?If yes how is it the best to do?

It's up to your taste but in case of doing it, replace R56 with a 100k pot ..
(OUT taken from wiper, of course..)